Long-chain fatty acids are essential for normal function of cell membranes and as precursors for neuroprotective and inflammatory molecules. For example, very long chain polyunsaturated fatty acids (VLPUFAs) are present in the human retina and play an important role in maintaining the structure and function of the retina. A disease with a defect in the gene that synthesizes VLPUFAs in the retina leads to an early onset degeneration of the macula and severe loss of vision. Many VLPUFAs and other very long chain fatty acids are not commercially available. Accordingly, there is a need to develop new methods for preparing long-chain fatty acids, including VLPUFAs. This application addresses this need and others.